How to read the observatory

A flight counts as a disruption if it was cancelled or arrived at least 180 minutes late. The threshold is not ours: Regulation (EC) 261/2004 provides for compensation for cancellation, and the Court of Justice of the European Union (Sturgeon judgment, 2009) extended it to passengers who reach their destination three hours or more late.

Legally, what counts is the moment the aircraft doors open; our archive records arrival as the flight data sources report it. It is always checked on the individual flight.

We count flights departing from the airports in the chosen scope, with any airline. That is the case in which the Regulation always applies: from an EU airport, whatever the airline. For flights arriving from outside Europe the Regulation applies only with a European airline, and the observatory does not mix them with the others.

It is the share of disruptions out of all flights that departed in the month. We look at the share and not the total because the number of flights changes with the season, and with the days the archive has: a share can be compared, a total cannot.

A day at an airport is an “event” day when, out of at least 20 departing and arriving flights, at least 50% were cancelled, diverted or arrived more than 120 minutes late. It is the same threshold we use to assess a claim.

When a whole airport stops, the cause is often external: an eruption, bad weather, air traffic control. If the airline proves extraordinary circumstances, and that it did everything it could to avoid their consequences, compensation is not due (Article 5(3)).

But not always. A strike by the airline's own staff stops an airport and is not an extraordinary circumstance (Court of Justice, Airhelp v SAS, 2021); and the burden of proof is on the airline, not the passenger. That is why the observatory never says “not owed”: it is checked flight by flight.

The rankings have two columns. “Disruptions” is the share for the whole month; “Excl. events” leaves out flights that departed from or arrived at an airport on the day it was at a standstill. The rankings are sorted excluding events: that is the everyday disruption, the one that says most about an airport, an airline or a route.

The archive sometimes has gaps: a day not read, or read only in part. A day counts if it has at least half the flights of a typical day of the month; a month is published if it has at least two thirds of its days. Missing days are listed next to the month, and the figures are those of the days we have.

We compare a month with the same month of the previous year, never with the month before: August against July would say more about the holidays than about delays. The comparison appears when the archive has both months.

It does not know why a flight was late, nor when a cancellation was announced: with at least fourteen days' notice no compensation is due. So it does not say whether your flight is owed anything. To find out, look up your flight: we look at that flight, with its times and what happened around it.